Newbie Hard Drive Question

Okay, so this might seem like a stupid question, but humor me...
I was surfing through some threads, and I came upon one about hard drives for powerbooks...the owner of a powerbook wanted to get a new HD because his/hers was failing. Other people responded about different types of HDs they thought were good (seagate, hitachi, fujitsu etc...)
Whoa. Wait. This is where I got confused.
I was under the impression that a computer is made ENTIRELY by a single company (ie: all the components are from that company as well).
Well, much to my surprise, apparently, they are not.

I'm assuming that if the HD is not made BY apple, but by another company, then other stuff on/in the computer is made by a different company, purchased by apple, and then installed. Am i right ?
So then, aside from the software, OS, etc...what IS made by apple?
And for that matter, what typically ISN'T? (made by apple, I mean)

And lastly (forgive my ignorance), you can put a different HD in your old computer (ie: Ibook, PB) and it will work just fine?

Duff-Man says....yes, in fact almost *all* the parts in your Mac are made by someone else. Apple designs things and contracts the building and assembly out...and again, yes, if it is a compatible hard drive you can use it in another Mac although keep in mind with laptops changing hard drives is not for the timid or inexperienced....oh yeah!

As Duff-man says (ouch), Apple physically manufactures nothing in their computers anymore. They used to do assembly of some machines at their own factories (Ireland and California, if memory serves), but I don't think they even do that anymore.

Some of the individual parts are *designed* by Apple--a few logic chips, no doubt, the motherboard definitely, the case of course, the power supplies, and now Apple is designing its own trackpads and scroll wheels (on the iPod). But even in all these cases, they just design the part then contract with a company in Taiwan (or elsewhere) to manufacture it. Those custom parts, along with a bunch of more-or-less off-the-shelf parts (hard drives, optical drives, graphics processors, the main processor, display screens, and the majority of the individual chips inside), are then sent to another Taiwanese company to be assembled into the finished comptuer.

Apple is a big enough company to have a few customizations to standard parts--for example, their optical drives usually have slightly customized Apple-specific firmware (in a handfull of cases actually disabling features to match Apple's standard specs that were based on older drives), hard drives generally at least have an Apple-specific label though they are mechanically identical, and of course Apple had a hand in the design of the PowerPC processor (that'll change with the Intel switch). The biggest example are the graphics cards which must have Apple-specific modifications to work, though the actual processor is identical to everything else by ATI or NVIDIA But even in these cases there's usually little if any actual difference from off the shelf parts.

The bottom line, of course, is that Apple usually picks good parts, designs what they can't get off the shelf, and contracts with good companies to assemble the stuff, so they're good computers and unique to Apple.

The advantage is that, with the exception of graphics boards (and that looks to be changing soon) pretty much everything is useable off the shelf--RAM and hard drives are just standard parts and almost anything should work.

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